Vacuum tube socket



Jan. 17, 1939. A. w. BARBER VACUUM TUBE SOCKET Filed Dec'. 3, 1935 [N VENTOR Patented Jan. 17, 1939 UNITED STATES PATENT OFFICE 4 Claims.

This present invention of mine concerns improvements in vacuum tube sockets. It particularly relates to methods of, and means for embodying by-passing capacity in a vacuum tube socket adapted for use at high radio or ultra frequencies.

One object of my invention is to provide a vacuum tube socket embodying by-passing capacity for several tube elements. Another object is to provide this by-passing to the tube mounting clips themselves thereby providing a shorter path for by-passed currents than was formerly possible. Still another object is to provide a rugged, simple socket construction with metal as the principal socket material. A further object is to so construct a metal socket as to provide an external screen and shield for the tube and its associated circuits.

In the past thermionic vacuum tube sockets have been constructed principally of some form of insulating material holding clips for receiving the tube base pins. This construction was used since the function of the socket was to provide a mechanical support for the tube and its electrical connecting means in the form of tube pin receiving clips. The by-passing required by the circuits embodying the tube was provided by discrete condensers attached to the pin receiving clips. The external tube screen or shield was provided by shields attached to the tube or the chassis holding the tube socket.

I have invented a new socket in which the circuit by-passing and the tubes external screen and shield are provided by the socket itself. The tube receptacle clips are in the form of flat strips terminated at one end by a spring for receiving the tube prong and at the other end by a lug suitable for soldering to circuit leads. The flat part of the clips is held between two pieces of metal from which it is insulated by means of some thin, high dielectric constant material such as mica. If the two metal pieces are grounded, a by-passing capacity is formed to the tube clips. One of the pieces of metal is in the form of a plate having a hole in the center thru which one end of the tube passes. In this way the socket acts as an external screen and shield for the tube and if the plate is made large enough, it may also be used to shield the input and output circuits associated with the tube. This construction is very useful at very high radio frequencies since at these frequencies even short leads to by-pass condensers have considerable impedance and by providing the by-passing capacity to the tube mounting, clips themselves, the

effective lead length from the tube elements to the by-pass capacity is reduced to a minimum. The construction also simplifies circuit construction by providing in the socket itself elements otherwise required as additional apparatus. 5;

The appended claims set forth, in particular, the novel features to be found in this invention. The following description, however, when taken in connection with the drawing, will serve to set forth the theory and mode of operation of 10' my invention.

In the drawing,

Fig. 1 shows a top view of my new socket.

Fig. 2 shows a cross-section of the socket with a tube in place.

Fig. 3 shows an equivalent circuit of the tube and socket.

Fig. 1 shows a top View of my new socket in which I is a metal base plate, 2 is a lower insulating ring, 3 are tube mounting clips, 5 is an upper insulating ring, 5 is. an upper metal plate, 6 are bolts or rivets, I is a central hole for receiving the tube envelope, 8 are lead holes in the base plate and lower insulating ring and 9 are socket mounting holes in the metal base plate. The metal base plate I serves as the foundation for the socket and forms one of the grounded sides of the capacity to the tube mounting clips. This capacity is between clips 3 and the plate I thru the lower insulating ring 2. 80 In order to make this capacity large, this ring should be thin and of material having a high dielectric constant. Mica has these properties and is mechanically strong and I have found it to be a very satisfactory material for the insulating ring 2. Another capacity to the tube clips is thru the upper insulating ring 4 to the upper metal plate 5 and here again mica is a satisfactory insulating material. By clamping the upper metal plate to the lower metal plate by means of the bolts or rivets B, an electrical connection is made paralleling the two capacities to the tube clips and the clips are pinched between the assembly thus holding them in place. In order that the clip to metal plate capacities may be as large as possible, the body of the clips 3 should be broad and fiat as shown. The inner ends of clips 3 are formed into springs ll suitable for receiving and holding the vacum tube prongs, while the outer ends 10 are formed and may be punched to form lugs suitable for soldering to wires leading to the external circuits. The base plate I has a central hole 1 large enough so that the vacuum tube bulb may be passed thru it but it should fit close enough to complete, by means of 55 plate I, the external screening of the tube. In order to be effective as a screen, the hole 7 should be about five to ten percent larger than the tube envelope as will be more clearly seen in connection with Fig. 2.

Base plate I mayhave holes 8 located directly under the lugs ill to permit the passage of lead wires to the lugs. It is also convenient to provide base l with holes 9 near the corners for mounting the socket.

I have found it possible to obtain a capacity of several hundred micro-microfarads between each tube mounting clip 3 and the ground plates I and 5. The effectiveness of these capacities as radio frequency by-pass means may be seen from computing the reactance at a given frequency. For instance, at 100 megacycles 200 micro-microfarads has a reactance of only 8 ohms. Also, since the reactance of only 2 centimeters of 16 gage wire is about 8 ohms, the socket clip capacities are more effective than any amount of external capacity could be if the leads to it are more than 2 centimeters long. The advantages of the tube clip by-pass become greater as the frequency is increased. On the other hand, external capacities may be added for the lower frequencies giving efiective by-passing over as great a range as may be desired.

In Fig. 2 I have shown a cross-section view of .my socket along a cut on the diagonal ab of Fig. '1. This shows the relation of the various parts of the socket and of the tube l2. Tube 52 is a typical pentode tube designed for high radio or ultra frequency circuits. The heater, cathode, screen grid and suppressor grid leads are brought out to radial pins it which should be by-passed to ground for efficient tube operation. The control grid and plate are brought out to pins at opposite ends of the tube envelope at it and I1 respective- ,ly. The screen grid is located between the control grid and suppressor grid within the tube. The internal element or ring it in the tube l2 forms a part of the screen system and an eX- ternal screen should be provided to complete the .tube screening. TlL s external screen is provided in my socket by hole I in plate I by reason of its close approach to ring it as shown at point 18.

The cross-section view of Fig. 2 also shows clearly the vertical relations of lower plate I, lower insulating ring 2, tube mounting clips 3, upper insulating ring l, upper plate or ring 5 and the clamping bolts or rivets E. The spacing of the bolts or rivets 6 around the socket should be chosen to provide as uniform as possible squeeze pressure on all the tube mounting clips 3 so that they will not slip out of place while in use. I have found that four equally spaced bolts plus a fifth located between the pair of clips gives a satisfactory pressure distribution as shown in Fig. '1. Fig. 2 also shows how the tube pins l3 fit into the formed ends it of the clips 3. t also shows how a lead wire l5 may be passed thru the lead hole 3 in the lower plate and insulating washer and how it may be soldered to lug it which forms the outer end of clip 3. The socket mounting hole 9 is also indicated.

Fig. 3 shows a circuit equivalent to the combination of tube l2 and my new socket. Tube i2 is shown as a pentode having cathode heater l9, cathode 253, control grid 2!, screen grid 22, suppressor grid 23 and plate 24. The control grid connection pin it is shown as is the plate connection pin ll. The tube elements I9, 20, 22 and 23 are connected to radial pins l3 which fit into the spring elements H which form the inner ends of clips 3. The capacities 25 and 2B represent the tube mounting clip to metal base plate and clip to upper ring capacities. The metal plate and ring are represented by the grounds G. These two capacities are formed to the clips receiving the tube pins connected to the tube elements I9, 2|], 22 and 23. It Will also be seen from Fig. 3 that the clip to base plate and upper ring capacities 25 and 26 are eifectively in parallel when the plate and ring are electrically connected together.

Many modifications of my socket are possible without departing from the spirit and scope of my invention. For instance the lower metal plate I may be round or it may have any one of a variety of shapes. Clips 3 may be longer or shorter and may cover a diiferent radial angle. The upper metal plate 5 may be made in sections suitable for holding one or more clips to the lower plate I. Other materials than mica may be used for the insulating rings. The insulating rings may be made in sections suitable for insulating one or more tube clips. By making the ground plate I sufficiently large, it may be used as a static and magnetic shield partition between the input and output circuits associated with tube l2. The use as a shield partition will be especially useful at very high radio frequencies since at these frequencies the circuit elements are physically small.

For use with a triode tube the socket may be modified by insulating the grid and plate mounting clips by low capacity means such as insulating members mounted in a cut-out section of the metal plates.

It will be apparent to one skilled in the art that many other modifications are possible in my socket construction without departing from the spirit and scope of my invention as set forth, in particular, in the appended claims.

What I claim is:

l. A thermionic vacuum tube socket comprising two metal plates, a plurality of tube pin retaining means, insulating members located between said means and said plates, means including said plate for clamping said plurality of tube pin retaining means, a hole in one of said plates adapted to pass the tube envelope and thereby adapting said last-named plate to form an external electro-static shield for said tube.

2. A thermionic vacuum tube socket comprising two metal plates, a plurality of tube pin retaining means, insulating members located between said means and said plates, means including said plates for clamping said plurality of tube pin retaining means, a hole in one of said plates adapted to pass the tube envelope and thereby adapting said last-named plate to form an external electro-static shield for said tube, and lead holes in said last-named plate located below the outer ends of said tube pin retaining means.

3. A pentode vacuum tube socket including a metal base plate, two annular insulating members, an annular metal member and tube pin mounting clips, said clips being located between said insulating members and said insulating members being located between said base plate and said annular metal member, a plurality of electrical-mechanical connections between said base plate and said annular metal member, a central hole in said base plate adapted to receive the tube envelope and thereby adapting said base plate to form an electro-static shield for said tube, socket mounting holes in said base said annular insulating members located near the outer ends of said clips.

4. A tube socket including a metal base plate, an annular metal member, two annular insulatlng members and a plurality of tube pin clips, means for clamping said clips between said insulating members and for clamping said insulating members between said annular member and said base plate and including electrical conducting means connecting said annular metal member with said base plate, and a hole in said metal base plate slightly larger than the tube envelope adapting the metal base plate to complete the external screening and shielding of the tube.

ALFRED W. BARBER. 

